Silicon oscillators are replacing crystal oscillators for a clock signal generator to a system-on-chip (SOC). A silicon oscillator requires less power-up time as compared to a crystal oscillator. The silicon oscillator further occupies lesser area compared to the crystal oscillator as additional timing components are not required. The silicon oscillator is usually implemented as a relaxation oscillator. The relaxation oscillator generally operates by charging and discharging a capacitor to a set of predefined reference voltages. The reference voltages are fed to a comparator as input to detect if the capacitor has been charged or discharged beyond the respective reference voltages. Output of the comparator is used to determine if the capacitor is to be charged or discharged.
However, the comparator takes a finite amount of time to generate the output, which is referred to as a comparator delay. Time taken by the capacitor to charge to the reference voltage is defined as charging time of the capacitor. Time taken by the capacitor to discharge is defined as discharging time of the capacitor. A sum of the charging time, discharging time, and the comparator delay equals an oscillation time period of the relaxation oscillator. Typically, an accurate relaxation oscillator requires that the comparator delay be reduced. High values of the comparator delay together with variation of the comparator delay due to fluctuations in temperature and supply voltage reduces accuracy of the relaxation oscillator.
In light of the foregoing discussion, there is a need for a method and system to reduce contribution of the comparator delay to the oscillation time period and thus, the oscillation frequency.